Miller's concept of electrophilic chemical carcinogenesis will be studied in case of four selected classes of significant pro-carcinogens 1) Polycyclic aromatic hydrocarbons 2) Aromatic amines and nitro compounds 3) Nitrosoamines and related compounds 4) Plant products of safrole- and aflatoxin-type. The nature of the active electrophilic agents will be determined under conditions allowing observations of stable long-lived carbocationic intermediates with methods previously developed in our laboratories, H1, C13 nmr and ESCA (photoelectron) spectroscopy will be used preferentially in these studies. The alkylating ability of carboncationic electrophiles formed by chemical activation of pro-carcinogens will be also studied in interactions with selected model target nucleophiles, such as nucleic acid bases and small peptides. These studies will also apply Fourier transform C13 nmr spectroscopy and ESCA spectroscopy for determination of the interacting sites. In the outlined studies new approaches will be followed to show possible in vitro electrophilic activation paths and interactions with model target molecules. These studies should help the biological scientists by providing a better up-to-date understanding of the in vitro aspects of studied classes of chemical carcinogens.